1. Field of the Invention
The present disclosure relates to liquid crystal display technology, and more particularly to a double layer LC FP Filter display device.
2. Discussion of the Related Art
Liquid crystal displays (LCDs) typically are characterized by attributes including thin, power-saving, and low radiation. Thus, the LCDs are widely adopted by a plurality of electronic devices, such as mobile phones, PDA, digital cameras, displays of personal computers or notebooks.
Currently, most of the LCDs are backlight-type LCDs. Generally, the LCDs include a housing, a liquid crystal panel and a backlight module arranged within the housing. The liquid crystal panel includes a color filtering array substrate, a Thin Film Transistor (TFT) Array Substrate, and a liquid crystal layer arranged therebetween. By applying driving voltages toward the two substrates to control the alignment of the liquid crystal, the light beams from the backlight module are reflected so as to display images. As the liquid crystal does not emit light beams itself, the backlight module is needed to provide the light source so as to display images. Thus, the backlight module is a key component of the LCDs. Generally, backlight modules can be classified into edge-type and direct-lit type according to the incident locations of the light source. Regarding the direct-lit type backlight module, the Cold Cathode Fluorescent Lamp (CCFL) or Light Emitting Diode (LED) are arranged behind the liquid crystal panel to form a surface light source. With respect to the edge-type backlight module, the LED light bars are arranged at lateral rear sides of the liquid crystal panel. The light beams emitted from the LED light bar enter one side of the Light Guide Plate (LGP). After being reflected and diffused, the light beams emit out from the light emitting surface and then operates as the surface light source of the liquid crystal panel.
FIG. 1 is an exploded view of the conventional LCD. The LCD includes a backlight module 100, a plastic frame 300 arranged above the backlight module 100, and a liquid crystal panel 500 arranged above the plastic frame 300, and a front frame 700 arranged above the liquid crystal panel 500. The backlight module 100 provides a uniform-radiated surface light source for the liquid crystal panel 500. The plastic frame 300 is for carrying the liquid crystal panel 500. The front frame 700 is for fixing the liquid crystal panel on the plastic frame 300.
FIG. 2 is a schematic view of the conventional liquid crystal panel. The liquid crystal panel includes a thin film transistor (TFT) substrate 502, a color filtering substrate 504 arranged opposite to the TFT substrate 502, a liquid crystal layer 506 arranged between the TFT substrate 502 and the color filtering substrate 504, and a first and a second polarizers 522, 542 respectively attaches to the TFT substrate 502 and the color filtering substrate 504. After being polarized by the first polarizer 522, the light beams from the backlight module enter the liquid crystal layer 506. Afterward, the polarized light beams selected by the liquid crystal layer 506 enter the color filtering substrate 504. A color filtering sheet 544 of the color filtering substrate 504 tunes the color of the light beams. The light beams are then polarized by the second polarizer 542 and are emitted out to display colorful images.
However, the polarizers and the color filtering sheet are key factors to the backlight efficiency. The overall optical efficiency may be in the range of between 5% to 10%. At the same time, the color range is also restricted by a color coordinate of the RGB color filtering sheet.
In order to overcome the above problems, FIG. 3 shows a conventional double layer liquid crystal FP filter display device (“display device”). The display device includes a backlight module 30, and a pixelated double layer LC FP filter module. The backlight module 30 includes a plurality of LED light bars 38 having RGB LED chips, a light guiding plate 36, a diffusion plate 34, and a transmission enhanced film 32. The backlight module 30 is for providing the backlight for the pixelated double layer LC FP filter module. The pixelated double layer LC FP filter module includes a first pixelated single-layer LC FP filter module 10 and a second pixelated double-layer LC FP filter module 20. Each of the filter modules include a plurality of pixel cells being arranged in an array. The pixel cells in each layers are independently driven to emit pixels with an non-shifted central wavelength. The pixelated double-layer LC FP filter module is for modulating the grayscale and the color of the backlight.
Referring to FIG. 4, the pixel cell includes a first substrate 111 and a second substrate 112 respectively arranged above and below the pixel cell, an up multi-layer dielectric reflective layer 113, a down multi-layer dielectric reflective layer 114, and a LC layer between the up multi-layer dielectric reflective layer 113 and the down multi-layer dielectric reflective layer 114. The LC layer is divided into a red pixel LC layer 152, a green pixel LC layer 154, and a blue pixel LC layer 156 by an insulated layer 150. A red pixel upper-layer electrode and a driving circuit 162, a green pixel upper-layer electrode and the driving circuit 164, and a blue pixel upper-layer electrode and the driving circuit 166 are arranged between the first substrate 111 and the second substrate 112 for providing driving voltage to the red pixel LC layer 152, the green pixel LC layer 154, and the blue pixel LC layer 156. During operations, the pixels opposite to each other in a vertical direction are supplied with different voltages by respective driving circuit such that the transmission spectrum of one pixel shifts toward the long wavelength and that of the other pixel shifts toward the short wavelength. Thus, the sub-pixels with non-shifted central wavelength is obtained by overlapping the projected transmission spectrums. In this way, the backlight grayscale is adjusted and the central wavelength of the emitted light beams is not shifted such that the backlight efficiency is enhanced.
However, as the transmission peak wavelength of one single sub-pixel corresponds to the central wavelength of the LED light bar of the backlight module, the peak wavelength of the transmission spectrum and the transmission rate of the sub-pixel cannot be adjusted. In addition, the transmission peak wavelengths of the sub-pixels relate to mixing the three primary color. The color range is small and cannot meet consumers' demand.